Another possibility is EMG, which uses electrodes to monitor facial muscles to control a computer pointing device [6], [14]. An analysis of an EMG interface according to Fitts’ law is shown in [16]; this interface provides discrete direction movements (horizontal and vertical separately) not diagonal.
Sip-and-puff is an option for people with tetraplegia mainly to control power wheelchairs [15], but this is usually difficult to operate and usually works only with four discrete directions.
Voice commands can be useful to access some computer and smartphone applications, but they are not adequate to direct control pointing devices. Some research studies use voice commands to control power wheelchairs [15], [17]. A way to improve the precision of the voice recognition system in noisy environments is lip-reading(speechreading), an image processing technology to identify speech from lip images [18].